A device of the above-described type is known from the article "The fibre Fabry Perot sensor" (J. Scheider et al., Clin. Phys. Physiol. Meas., 1990, vol. 11, No. 4, 319 through 325). The optical fiber of the pressure sensor is in this case connected via two fiber-optic light guides to the recording unit. Using the first fiber-optic light guide, light from the light source is sent into the optical fiber, and the second fiber-optic light guide serves to feed back the measuring signal from the Fabry Perot measuring section to the recording unit. Therefore, the two fiber-optic light guides are connected to the opposite ends of the optical fiber. Accordingly, the optical fiber or one of the fiber-optic light guides must be bent to a small radius and located in the catheter. Coupled with this is an extraordinary mechanical strain on the optical fiber or the fiber-optic light guide. A relatively high frequency of breakages is the result. This is diametrically opposed to the functional reliability of the device, particularly necessary when the device is to be used for lengthy examinations.
With a different device for the manometric measurement of the oesophagus, the catheter has mechanical pressure sensing elements. Piezo crystals are essential components of these pressure sensing elements. The piezo crystals of the pressure sensing elements are connected via electrical lines to a recording unit. A disadvantage with the mechanical pressure sensing elements is that they are only suitable for local measurement of pressures. This means that the pressure sensing elements must be precisely arranged at the point where the pressure which is to be measured occurs. However, this is virtually impossible during lengthy examinations, especially with manometric measurement of the lower oesophagus sphincter. The position of the musculature which seals off the stomach alters with respect to the catheter during strong breathing movements such that examining them using a mechanical pressure sensing element can no longer be undertaken.